1. Field of the Invention
The present invention relates to an image-forming apparatus such as copiers, facsimiles and printers, in which an image is formed by electrostatic copying process, a process cartridge which is provided in the image-forming apparatus, and an image-forming method which is used for the image-forming apparatus.
2. Description of the Related Art
The method for visualizing image information via latent electrostatic images, for example, electrophotography is now used in various fields. In electrophotography, a latent electrostatic image is formed on a photoconductor by charging and exposing, the image is developed with a developer containing toner, and visualized via transferring and fixing. The developers used herein are a two-component developer consisting of a carrier and a toner, and one-component developer consisting of a toner alone such as magnetic toner. The two-component developers have advantages of good controllability and are now used extensively, because a carrier takes charge of the functions of stirring, conveying and charging developers, and functions are separated as a developer. Especially, the developer containing a carrier coated with resin is excellent in charge control property and relatively easy to improve environmental dependency.
In a two-component developing apparatus, a toner and carrier contained in a developer container in a developing device. After the toner and carrier are stirred and frictional charged, a latent image on the latent image bearing member is developed by supplying a latent image bearing member such as conductor with the frictional charged toner and carrier by means of a developer bearing conveyer such as developing roll.
During the development of the latent image, the toner in the developer container in the developing device decreases in accordance with consumption, on the other hand, the carrier is not consumed and remains in the developer container. Therefore, the carrier is more frequently stirred in the developer container in comparison with the toner, and accordingly the ratio of the degraded carrier increases. If the ratio of the degraded carrier increases in the developer container, the charge amount of the toner will be unstable, and troubles occur, for example, image degradation is induced.
Conventionally, to suppress the image degradation due to carrier degradation as the above description, so called “trickle developing system” is proposed, that is, not only the toner but the carrier are appropriately supplied to the developer container, in addition, owing to supplying the carrier the excess two-component developer in the developer container is recovered (Japanese Patent Application Publication (JP-B) No. 2-21591).
The trickle developing system is that the degraded carriers are replaced by supplying new carriers in a developing device or a developer containing portion as well as the decreased toners are refilled. Refill and recovery of the two-component developer containing the carrier enable the degradation of the carrier in the developing device or a developer containing portion to be suppressed, and the constant developing properties of the two-component developer are maintained, and thus the image degradation caused by the fluctuation of the developing properties of the developer can be suppressed.
The developer, which is supplied to the developing device or the developer containing portion, is filled in a supplying device which is provided separately from each developing device. The developer is supplied to each developing device depending on the consumption of the developer in accordance with forming images.
In the above-described trickle developing system, the following systems are carried out: the system in which the toner and the carrier are independently supplied to the developing device, and the excess developer in the developer tank is recovered (for example, Japanese Patent Application Laid-Open (JP-A) No. 9-204105); and the system in which the toner and the carrier are preliminarily mixed, and the mixture of the toner and the carrier is filled in the supplying device, and this developer is supplied to the developing device (for example, JP-B 2-21591).
Among these developer supplying systems, in case of the former, there is a problem that the developer must be supplied after the mix ratio between the toner and the carrier is adjusted, thus the control is complicated.
On the contrary, in case of the latter, in the developer supplying device, the toner and the carrier are preliminarily in a mixed condition in the developer supplying device, the complicated process of the adjustment of the supplying ratio between the toner and the carrier is not needed, and moreover the device can be simplified.
However, in the latter system, a big difference in specific gravity between the toner and the carrier leads to the state that each of them tends to exist disproportionately when both are mixed and filled in the developer supplying device. In addition, as the toner and the carrier are different in flowability, the supplying properties are different between the toner and the carrier, when the developer is supplied from the developer supplying device to the developing device, the supplying ratio of the toner and the carrier fluctuates. If the supplying ratio of the toner and the carrier fluctuates, the charge amount of the carrier is variable in the developing device, and then the problem occurs that the stable developing property cannot be obtained.
To obtain the stable charge amount of the toner in the developing device, the developer must be supplied to the developing device with the ratio between the toner and the carrier therein at a constant rate.
As a unit which makes the toner and the carrier to be existed uniformly in the developer supplying device, for example, there is a method that the developer supplying device with a stirring member in the supplying device is used, and by the stirring member the toner and the carrier are stirred and mixed.
Japanese Patent Application Laid-Open (JP-A) No. 2004-29306 discloses a developer supplying device, or a cylindrical developer supplying device in which a spiral projection along the surface of the inner circumference, contains a developer supplying container having an opening portion to discharge a contained developer, which contains at least a projected rim provided to project from the inner wall to inward and form spirally toward the opening portion, and the developer which is transported by the projected rim in accordance with the rotation of the developer supplying container is supplied from the opening portion to the developer receiving device.
Japanese Patent Application Laid-Open (JP-A) No. 2004-264510 discloses a filling device providing a spiral screw by the name of auger. Specifically it discloses that the toner container in which a moving member such as a screw by the name of auger or a coil spring is provided, and a cylindrical toner container, so called screw bottle 15, in which a spiral projection 14 is formed along the surface of the inner circumference thereof.
In the filling device disclosed in Japanese Patent Application Laid-Open (JP-A) No. 2004-264510, by driving rotationally the rotation axis of the moving member, the toner in the developer supplying device is transported to the direction toward the outlet, and discharged from the outlet then supplied to the developer supplying portion.
By using these supplying device with the moving member, or the developing device in which the supplying device itself rotates, the developer in the supplying device is discharged absolutely without the remaining amount thereof additionally, the discharged developer can be surely transported to the developing device, the developer in the apparatus can be adequately stirred and mixed, then the toner and the carrier can be in the state of uniformly dispersed.
However, in case that the developer is stirred and mixed in the supplying device, the carrier deteriorates before supplied to the developing device. Therefore, it fails to obtain sufficiently the effect of trickle developing system that is the developing properties of the two-component developer can be constantly maintained by supplying the carrier before deterioration to the developing device.
Recently, the developer supplying device with the system that discharging mechanism such as an auger and a screw bottle is not contained in a toner container is proposed.
For example, Japanese Patent Application Laid-Open (JP-A) Nos. 2001-324863 and 2002-72649 disclose that the system with the toner in the pouched flexible container is suctioned with the suction pump, and supplied to the developing unit and it is already commercially available. These inventions disclose that the container can reduce its volume, that is the state of deflating a container by suctioning the toner therein after the toner is discharged from the container.
As described above by using the supplying device which does not have a stirring unit therein, the problem such that the carrier is deteriorated before supplying the developing device will not occur. A small-footprint device body can be realized, and in addition, at the time of recovery the amount of recovery per unit volume can be reduced compared with using a hard bottle for disposal.
However, as described above, when the developer which consists of the toner and the carrier and is filled in the developer supplying device without containing a stirring unit is supplied to the developing device, for example, in case that the developer outlet is provided on the lower side of the supplying device body, the carrier with heavier specific gravity moves easily to the lower side. Thus the phenomenon is likely to occur that the toner and the carrier disproportionately exist in the developer supplying device. When the property of the flowability differs largely between the toner and the carrier, the supplying property between them differs largely and the problem occurs that the stable charge amount of the toner cannot be obtained in the developing device.